Change add to cart button text

functions.php

<?php
//* Do NOT include the opening php tag shown above. Copy the code shown below.

//* Change add to cart button text single product page
add_filter( 'woocommerce_product_single_add_to_cart_text', 'wps_custom_cart_button_text' );

function wps_custom_cart_button_text() {

  return __( 'Buy Product', 'your_theme_text_domain' );

}